1. Technical Field
The present invention relates to clamps and, more specifically, to midline clamps for supporting lengthy, self-supporting, all dielectric, telecommunication cables at spaced intervals. More particularly, this invention relates to a cable gripping clamp for retaining cables in tension at spaced intervals such as those formed with a multiplicity of continuous fibers, such as glass fiber optics and high modulus synthetic strength member of aramid fibers, having one or more non-metallic plastic sheaths thereover.
2. Background Information
While numerous types of clamps have been used previously in terminating ropes and cables to maintain such flexible continuous lines in tension, modern day telecommunication cables comprised of a substantial number of continuous individual fibers bundled together into a single cable must be supported at intervals without termination. It is highly desirable to support such lengthy cables at spaced intervals without interconnection or termination which junctions are highly labor-intensive in their formation.
Certain types of terminating clamps have heretofore employed a wedging action wherein the greater the amount of tension on the cable, the tighter the clamp will grip the cable. However, such gripping action must be carefully controlled in the use of midline clamping of telecommunication cables to avoid undue compression and abrupt angular bending of such cables to prevent any damage, distortion or breakage of any of the individual fibers during retention of the cable in very severe environmental conditions. Normally, in the use of wedge-type termination clamps, a tapered plug element is mounted on the cable with a complementary sleeve member mounted thereover to support a limited portion of the cable most commonly at its end or near a termination point. Such components are generally cylindrical in shape and may be slipped over the terminating end of the cable in a prescribed order of joinder. The components are fully cylindrical in an uninterrupted annular configuration and cannot be joined to a cable at midpoints where the cable is fully integral and uniformly continuous throughout a great length.
One type of rope clamp construction is disclosed in U.S. Pat. No. 4,509,233, such clamp being utilized at the termination of a rope or cable for supporting the same at a termination or connection point which will not damage or distort the continuous fibers which make up the interior body of such ropes or cables. Such clamp is of particular value in mounting ropes or cables comprised of a plurality of synthetic continuous fibers at a desired terminus; however, in supporting or mounting of modern day telecommunication cables in elevated relation, their terminations are located at substantial distances apart measured in miles requiring the continuous cables to be supported at spaced intervals measured in hundreds to thousands of feet in elevated tensioned relationship between points of delivery and use of conveyed technical information, such as telephone lines and coaxial cables for video pictures, computer data, and the like.
While a number of the prior clamp constructions are capable of satisfactory performance for supporting certain types of heavy-duty cables such as metallic electrical lines for transmission of electrical power, many of such clamps are not capable of supporting highly-sophisticated telecommunication cables which are formed from a multiplicity of very fine individual fibers such as glass fiber optics and aramid fibers which are located within an annulus of aramid material and surrounded by an outer protective plastic jacket. Such cables are formed having very great lengths with substantial numbers of individual fibers packed closely into a cylindrical bundle having one or more plastic layers thereover forming the exterior covering of the cable. The cable is normally extremely flexible having a very high strength-to-weight ratio, but due to its extremely sophisticated fragile nature, only relatively small compressive forces may be applied over limited intermediate areas of the cable which are normally supported in tension. The intermediate area employed to retain the cable is gripped with sufficient compressive force to support the cable in tension even though the particular amount of tension may vary rather widely throughout the operating or useful life of the cable.
Most prior art clamps exert strong compressive forces on the cable over small localized intermediate areas which can cause the individual fibers to be damaged or stressed adversely which will result in breakage or serious disruption of the information carrying capabilities of the fibers. Other prior art clamps exert a very low compressive forces over an extremely long area of cable. The length of the clamp may be as long as 75 times the diameter of the cable. These helical wrapped clamps are extremely unwieldy and difficult to apply to this flexible cable.
There has been a special need for a user friendly midline clamp construction which will provide distributed compressive forces over generally lengthy intermediate areas of the cable to maintain the cable in generally axial relation. Such distributed forces prevent damage to the fragile fibers in a transverse direction and maintain sufficient gripping force on the cable when the tensional forces on the cable are varied through considerable limits. When the cable is mounted outdoors in widely-varying climatic conditions, it must be capable of durably withstanding high winds and accumulations of snow and ice over a long working life with little or no maintenance.